Current-limit relay



Aug, 31 1926. 1,598,231

T. ZWEIGBERGK CURRENT LIMIT RELAY Filed Dec. 20. 1923 1 3p :2 Jill 515122 01:

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UNITED STATES PATENT OFFICE.

THORSTEN ZWEIG BERGK, OF LONDON, ENGLAND.

CURRENT-LIMIT RELAY.

Application filed December 20, 1923, Serial No. 681,720, and in Great Britain .lune 20, 1923..

Relay switches which are used for controlling'or limiting current in a main or service line generally embody in their construction arriron armature actuated or at tracted by an electromagnet, the movement of the armature being utilized to open or close the switch contacts. Such relay switches are not satisfactory for current regulating purposes where it is desired to obtain close regulation, as the ordinary electromagnet and iron armature arrangement is not sufficiently sensitive in response to slight variations in current flow in the electromagnet. This is due primarily to variation in 1 the magnetic reluctance of the iron circuit as the iron armature moves closer to the electromagnet. This movement increases the effective magnetic lines acting on the armature with the result that the armature will not drop away from the electromagnet unless the amount of current in the electromagnet becomes considerably decreased after the armature has once been attracted by the electromagnet.

The object of the present invention therefore is the provision of a current limit relay switch which is extremely sensitive in its response to variations in current flowing in the electromagnet of the switch mechanism. To

this end I increase the sensitiveness of'an ordinary electromagnetically controlled current limit relay switch by connecting an auxiliary winding in the nature of a, moving coil across the winding of the electromagnet whereby the coil may be attracted by the magnet and in its approach to the electro-' magnet will not thereof.

A further object of my invention is the (0 provision of a simple, compact, commercially practical electromagnetic current relay switch construction which may fulfill the foregoing objects.

Other ob 'ects of my invention will herein after be set forth in the following description referring to the accompanying drawings which illustrate a preferre embodiment thereof. The essential characteristics are summarized in the claims.

Fig." 1 is a bottom Ian view of a current limit relay switchem odying my invention; Fig. 2 is a cross sectional elevation taken through the center of the electromagnet as alter the magnetic circuit indicated by the. line 2-2 of Fig. 1 and showing the. mechanism with the relay switch contacts open; Fig. 3 is a view similar to Fig. 2 with the relay contacts closed.

Referring to the drawings, in Fig. 2, 5 represents a main coil, disposed about a metallic core 6 whiclris carried by an external iron yoke 7, comprising the frame or body got the switch. The frame 7 is provided with a pair of downwardly extending arms 8 which comprise a support for a pivot pin 9 upon which a switch arm 10 is mounted. The switch arm 10 has an upwardly extending portion 11 provided with an extension 12, formed of fiber or other suitable insulating material. This extension supports a contact bridge 13 which is pivotally mounted upon a small bracket 14 secured to the extension 12. The contact bridge 13 is positioned to span contacts 15 and 16 which are mounted upon an insulating block 17 se-' cured to the upper part of the iron yoke 7. Line wires 18 and 19 lead to and \from the contacts 15 and 16 respectively.

The foregoing described arrangement is well known in the art, but the novelty of my device is to be found in the manner in which I electromagnetic-ally actuate the switch arm 10 while I maintain a uniform reluctance in the moving member. This I bring about by first forming the arm 10 of aluminum or other suitable non-magnetic metal, and then rigidly attaching to this arm a coil which may be connected across the line 20 of the main magnetic coil 5. I according] form the lower reach of the armor switch lever 10 to provide a cylindrical portion 22 which, when the arm 10 is mounted upon the iron yoke 7, will be substantially concentric with the core 6. The lower portion 6" of the core 6 is enlarged and arranged to extend into the cylindrical portion 22 of the switch arm 10 for a purpose to be presently described. Upon the upper end of the cylindrical portion 22, I mount an auxiliary coil 24 wherebythis coil may be adjacent the enlarged portion 6 of the core 6 when the relay is being maintained open by the electromagnet 5. This coil is connected by wires-26 and 27 across the lead wire 20 of the mainmagnetic coil 5. A weight 30, secured to the under side of the arm 10,

serves to cause the relay switch to close when the current in the main magnetic coil 5 drops. The relation of the parts under such a condition is illustrated in Fig. 3.

The operation of the switch is as follows: When the desired current is flowing in the lines 18 and 19, the contact bridge 13 is caused to rest upon the contacts 15 and 16 in the line 19 by the action of the weight 80 upon the arm 10. The current flowing in the main magnetic coil 5 and shunt coil 24 under this condition, is not suificient to set up sufficient flux to cause the weight 30 and the arm to be raised. 'If an excess or overload current flows in the lines 18 and 19, however, sutficient magnetic reaction takes place to cause the coil 2 to be attracted to the core 6 thus raising the weight 30 and effecting an opening of the switch contacts 13, and 16. This condition will prevail as long as an excess current is maintained in the main magnetic coil 5 and auxiliary coil 2st. If, however, the current is slightly reduced in the magnetic coil 5, the coil 24 will be re leased, the weight will cause the arm 10 to drop and thus effect a closing of the contact-s controlling the line 19.

The dropping or-releasing the coil 21 is immediately effected upon the slightest decrease of the required current flowing in the coil 5 as this drop is accentuated due to the decrease of the magnetic pull of winding 5 and to the reduced current flowing into the shunt winding 24, since the latter is connected across the main magnetic coil 5.

From the foregoing description of my invention, it will be seen that I may obtain an extremely sensitive current switch relay mechanism due to the fact that there is no change in magnetic reluctance of any of the moving parts regardless of the relative positions thereof. It is to be understood that my invention may be incorporated in a variety of devices directed to the relaying or regulating of current and that the switch mechanism illustrated in the drawings is preferred only as a simple, commercial embodiment of a current relaying switch.

I claim:

In a device of the character described, the combination of an iron shell having an internal core, a winding within the shell about the core, an ear projecting from the shell, a lever of non-magnetic material pivoted to the ear and having one arm projecting across the core, a cup-like extension of such arm projecting into the space between the core and shell, a winding about such extension, a contact carried by the other arm of the lever, and a terminal member insulatingly carried by the shell and in position to be engaged by said contact.

In testimony whereof, I hereunto afiix my signature.

THORSTEN ZIVEIGBERGK. 

